如何在Flutter中使用Android摄像头的后台？

dependencies:
  camera: ^0.10.0

import 'package:camera/camera.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final cameras = await availableCameras();
  final camera = cameras.first;
  runApp(MyApp(camera: camera));
}

class MyApp extends StatelessWidget {
  final CameraDescription camera;

  const MyApp({Key key, this.camera}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: CameraScreen(camera: camera),
    );
  }
}

import 'package:camera/camera.dart';

class CameraScreen extends StatefulWidget {
  final CameraDescription camera;

  const CameraScreen({Key key, this.camera}) : super(key: key);

  @override
  _CameraScreenState createState() => _CameraScreenState();
}

class _CameraScreenState extends State<CameraScreen> {
  CameraController _controller;
  Future<void> _initializeControllerFuture;

  @override
  void initState() {
    super.initState();
    _controller = CameraController(
      widget.camera,
      ResolutionPreset.medium,
    );
    _initializeControllerFuture = _controller.initialize();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Camera Example')),
      body: FutureBuilder<void>(
        future: _initializeControllerFuture,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            return CameraPreview(_controller);
          } else {
            return Center(child: CircularProgressIndicator());
          }
        },
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.camera),
        onPressed: () async {
          try {
            await _initializeControllerFuture;
            final image = await _controller.takePicture();
            // 处理拍摄的照片
          } catch (e) {
            print(e);
          }
        },
      ),
    );
  }
}